Electrostatic apparatus



Sept. 26, 1950 s. GILMAN ELECTROSTATIC APPARATUS Original Filed Feb. 9,1945 INVENTOR L i 0 G a z Y. M 3 5 Patented Sept. 26, 1950 UNITED,STATES PATENT OFFICE ELECTROSTATIC APPARATUS Original applicationFebruary 9, 1945, Serial No.

Divided and this application October 24, 1946, Serial No. 705,332

18 Claims.

This application is a division of my patent application, Serial No.577,021, filed February 9, 1945.

My parent application is directed to apparatus for removing foreignparticulate matter from a gas stream by means of equipment that producesan electrically charged liquid spray having a higher net electric chargethan was previously obtainable with similar equipment such as disclosed,for example, in G. W. Penney Patent No. 2,357,354, dated September 5,1944. Various embodiments are disclosed in the parent case. The instantapplication is limited to selected embodiments in which a charge isimparted to a liquid spray by the use of elongated electrodes.

Objects, features and innovations of my invention, in addition to thoseset forth in my aforesaid parent application, will be discernible fromthe following description which is to be taken in conjunction with theaccompanying schematic drawing, in which: c

Figure 1 is a vertical sectional view of an electrical dust-precipitatorembodying a form of my invention;

Figs. 2 and 3 are sectional views, taken substantially along the linesIIII and IIIIII, respectively of Fig. 1

Fig. 4 is a vertical sectional view of a further form of my invention;

Fig. 5 is a view showing another apparatus in accordance with myinvention, for producing charged sprays; and 7 Fig. 6 is an enlargedsectional view, taken substantially on the line VI--VI of Fig. 5.

The apparatus shown in Figs. 1, 2 and 3 comprises a rectangular gas duct68 in which is located a dust-charging or ionizing means A for charginggas-borne particulate matter, and a dust-precipitating means B on thedownstream side of the dust-charging means, for removing the chargedparticles from the flowing gas stream. Field affecting means Ccomprising a plurality of spaced grounded plates may be provided on thedownstream side of the dust-precipitating means B for preventing spacedischarges and for improving dust removal.

The dust-charging means A comprises a plunality of spaced groundedrelatively large tubular electrodes Ill, transverse to the gas stream,and between which relatively ilne ionizing wires 12 ar insulatedlysupported. Such a dust-charging means, or ionizer element, iscomparatively well known to the art.

The dust-precipitating means B comprises a 2 means being indicated inits entirety by the reference numeral 14. The charged-spray-producingmeans 14 comprises any suitable equipment which emits a liquid spray,and is shown as a 5 metallic pipe-member It provided with a plurality ofmetal nozzles 18 along its length. The tips of the nozzles are kept atground potential by grounding the pipe-member 16 or conductivelyassociating it with the gas duct 69 which is preferably of metal andalso grounded. The spray from the nozzles 18 passes between a pair ofspaced straight parallel semicylindrical electrodes 82 which aresupported on insulators 83 and are given a relatively high potentialthrough insulated conductors 84 connected to any suitable power source.Such a source is indicated schematically as a battery 85 having onterminal end grounded. The curved surfaces of the electrodes face thenozzles in the embodiment shown.

20 The potential-polarity of the ionizing wires 12 and the electrodes 82is the same and is opposite to that of the electrodes 10 and the nozzles18. The ionizing wires 12 produce charged matter in the spac betweenthem and the ground elec- '25 trodes Iii so that gas-borne particles arecharged.

Liquid fed to the pipe-member 16 comes out of the nozzles 18 as a spraywith its droplets charged because of the electrostatic field between thenoz- Zles and the electrodes 82. Consequently, each nozzle-tip fromwhich a spray emits is, in effect,

an electrode that is charged oppositely from the electrodes 82. Thespray droplets have electric charges of a sign or polarity which isopposite to that on the gas-borne particles so that the droplets andparticles attract each other in the region where they intermingle, thisregion being generally somewhat below the electrodes 82. Preferably thcharged spray spreads completely across a full transverse section of thegas duct,

40 at the field affecting means C. The effectiveness with which thespray droplets are charged, and hence the efficiency of thedust-precipitator in the embodiments described, can be increased bypreventing drops which collect on the electrodes 82 from continuallydischarging into the spray region or toward the nozzles 18, for reasonsmore fully described in my aforesaid parent application. To this end, inthe embodiments disclosed in Figs. 1, 2 and 3, the liquid dropscollecting on the electrodes 82 are caused to discharge toward means forproducing a charged-spray, the last electrode sumcient to electricallyforce the col- 3 lected drops on the electrodes to discharge toward theside 06 which functions as an electrode charged oppositely to theassociated electrode 02. After a drop on an electrode 02 discharges andbefore it recharges, it will fall from th electrode if the drop hassuflicient weight.

In Fig. 4, I show a further embodiment which is similar to that of Figs.1-3 but in which the action of gravity is utilized to help remove dropsfrom electrodes 90 that correspond to the electrodes 02 of Fig. 1.Electrodes 90 slope downwardly so as to caus drops thereon to tend toflow downwardly to the lowermost ends of the electrodes, away from thespray region so that they cannot discharge into the spray. Sloping theelectrodes permits the spacing between the electrodes and the parallelsides of the gas-duct to be greater than would be the case if theelectrodes were not sloped.

Figs. 5 and 6 show a further form of my invention in which straightparallel cylindrical elongated relatively insulated electrodes I00 areprovided between which a metallic spray-producing means I02 establishesa spray. In this embodiment, the spray-producing means has been shown aspneumatic and comprises a grounded liquid-supply pipe-member I04 and anair-supply pipe-member I06 connected to a plurality of spray nozzles I08having outlet tips H0. Liquid flows centrally through each sprayingnozzle via a passage II2. Air under pressure flows in a conical passageI which is around the passage 2 and is tapered to the outlet tip IIO forproviding a spray which passes between the insulated electrodes I00.

Ihe electrodes I00 are sloped as in the embodiment shown in Fig. 4.However, the lowermost end of each is provided with a small catch-basinI I6 having a drain-opening to which a drain-pipe H0 is connectedthrough which liquid collecting on the electrode may drain. Thedrain-pipe III is of a material providing a high resistance path alongwhich the draining liquid flows into a grounded container I20.

In embodiments usually utilizing a high resistance drain, the liquidremaining on the insulated electrodes, such as the electrodes I00, loseselectric charge by leakage so that the possibility of electricaldischarge from distorted liquid drops on the electrodes is greatlyminimized or entirely eliminated. In embodiments which do not use adrain, liquid on the electrodes can fall from them after they form largeenough drops on which the pull of gravity is greater than the forceexerted on them by the electrostatic field extending from the electrodeto the spray-nozzles and to the point at which the charge of the spraymay be considered to be concentrated.

I have found that the use of substantially straight electrodes, eithercylindrical or semicylindrical or some other cross-section, in equipmentfor charging a spray, is a considerable improvement over the ring-typeelectrodes, particularly if used with a plurality of spray-nozzles of apneumatic type along the lines shown, for example in Figs. 5 and 6.

Using a pneumatic nozzle, identified as type JPNF, set-up No. 12,described in a catalogue identified as Spraying System Nozzles andRelated Products, Catalogue No. 22 oi the Spraying System Company,Chicago, Illinois, an improvement of as much as 200% and above in thecharge given to the spray was obtained over that obtained in thespecific non-pneumatic type of spray-nozzle and ring electrode,specifically dethem. By sloping the electrodes about 20 to the,

horizontal, instead of keeping them horizontal. very effective drainingof collected liquid was provided, permitting a much higher voltagebetween the spray-nozzle and the electrodes before objectionable dropdischarges occurred.

The diameter of the straight electrodes and their spacing aflect thesize of the drops on the electrodes and the amount of charge that can begiven to the spray. With a constant voltage across the tubularelectrodes and the spray-discharge nozzle, increasing the separation ofthe electrodes aflects the field-gradient at the nozzle tip and at thesurface of the electrodes. The factors aflecting the field-distributionare, however, so varied and complex that an exact analysis is hardlypractical. Various grounded surfaces around the nozzle and therelatively insulated electrodes obviously will change the field lines.Even the character and angle of the spray have their eflect. However,experiments indicated that for a particular apparatus there appears tobe an optimum spacing for straight electrodes at which a maximum chargeis imparted to the spray.

While I have described my invention in connection with severalembodiments, it is obvious that its teachings have wide application andcan be applied in other forms or uses.

I claim as my invention: a

1. A device of a class described comprising, in combination, aduct-means for a gas-stream, charging-means for charging gas-borneparticles, a liquid-spraying device on the downstream side of saidcharging-means, an insulated electrodemeans in said duct-means spaced topermit the spray from said liquid-spraying device to pass in proximitythereto and then spread across the duct-means, and a high-resistancedrain for draining oiI liquid collecting on said insulatedelectrode-means.

2. A device of a class described comprising, in combination, aduct-means for a gas-stream, charging-means for charging gas-borneparticles, a liquid-spraying device on the downstream side of saidcharging-means, a sloped elongated electrode-means in said duct-meansspaced and insuiated from said liquid-spraying device, means foroppositely charging said liquid-spraying device and saidelectrode-means, and drain means from the lower end of saidelectrode-means.

3. Charging apparatus comprising a sprayingdevice having a plurality ofspaced points from which a plurality of sprays can be emitted, a pair ofspaced elongated parallel electrodes spaced from said points near outeropposite sides of the region for the sprays, said electrodes beingrelatively insulated from said points, and means for supporting saidelectrodes so as to substantially span the distance between said points,said electrodes being substantially straight, and sloping with respectto a line joining a pair of said points.

4. Charging apparatus comprising a sprayingdevice having a plurality ofhorizontally spaced points from which a plurality of pneumatic sprayscan be emitted, a pair of spaced elongated metal electrodes spaced fromsaid points near outer opposite sides of the region for the sprays, saidelecasaaeia.

and means for supporting said electrodes so as to substantially span thedistance between said points, said electrodes being substantiallystraight and supported so as to slope downwardly, said points beingspaced from a plane which Joins the edges of said electrodes farthestfrom said points, the points being spaced from said plane in a directionopposite to the direction in which the sprays leave said points.

5. Apparatus for providing a charged liquid spray, comprising aspraying-device having a plurality of horizontally spaced pneumaticsprayproducing nozzles having tips from which a plurality of sprays canbe emitted, and a pair oi. spaced separate electrodes spaced from saidtips and spanning the distance therebetween near outer opposite sides ofa region occupiable by the sprays, said electrodes being relativelyinsulated from said nozzles, said nozzles pointing between saidelectrodes and having their tips spaced from said electrodes in thedirection opposite to the spraying direction.

6. The invention of claim characterized by said electrodes beingsubstantially straight and sloping with respect to a line Joining a pairoi said points.

7. Apparatus for providing a charged liquid spray, comprising aspraying-device having a plurality of spaced pneumatic spray-producingnoz zles from which a plurality of sprays can emitted, said nozzleshaving tips, a pair of spaced substantially straight electrodes spacedfrom said tips both laterally and in the spraying direction and spanningthe distance therebetween, said electrodes being transversely curved atfaces located at outer opposite sides of a region occupiable by thesprays, said electrodes being relatively insulated from said nozzles,said nozzles pointing between said electrodes, additionalelectrode-means relatively insulated from said pair of electrodes, andarranged on a side thereof away from said region, and means foroppositely charging said electrodes with respect to said nozzles andsaid electrode-means, the spacing, configuration and charging-potentialsof said electrodes, electrode-means, nozzles and charging means beingsuch that the field gradient at said electrodes in a direction towardsaid region is less than the field gradient at a part of said electrodesiacing in a direction away from said region.

8. A device of a class described comprising, in combination, arectangular metallic dustmeans for a gas-stream, charging-means forcharging gas-borne particles, a liquid-spraying device on the downstreamside of said chargingmeans, a pair of separate parallel insulatedrodlike electrodes in said duct-means spaced to permit a spray from saidliquid-spraying device to pass therebetween and then spread across theduct-means, said electrodes paralleling opposite v said electrodes.

10. Means for producing a charged liquidspray comprising spray meansproviding a plurality of spray-emitting points arranged substantiallylinearly, insulated electrode-means ing with respect to the direction ofgas-flow past insulated and spaced. from said points of said spraymeans, said electrode-means comprising substantially parallel spacedmetal rod-like portions spanning the points, said portions beingunconnected in the spanning distance, said spray-emitting points 01 saidspray means being spaced from the plane nearest thereto which includessaid metal portions of said electrodemeans, a second electrode-meanscomprising sections insulated from said portions and located near a sidethereof away from said points, and means for oppositely charging saidinsulated electrode-means and said spray means, and for oppositelycharging said insulated electrodemeans and said second electrode-means,the spacing, configuration and charging potentials being such that thetendency of the field gradient at said insulated electrode-means in adirection toward said spray means to cause liquid-drops on saidinsulated electrode-means. to deform and discharge toward said space, isoverbalanced.

11. Means for producing a charged spray comprising a pair of elongatedparallel metal electrodes, spraying nozzle-means having a sprayingnozzle-tip insulated from said electrodes, said nozzle-tip being nearthe plane nearest thereto which includes a part of each of saidelectrodes, but lying on a side of said plane directed away from saidelectrodes, said nozzle-tip being directed to provide a spray in thespace between said electrodes which spray is chargeable by an electricfield between said nozzle-tip and said electrodes, said electrodesextending lengthwise beyond the nearest point of said nozzle-means for adistance greater than the distance of said nearest point to either ofsaid electrodes.

12. Charged-spray-producing means as defined in claim 11 but furthercharacterized by said electrodes being sloped from the direction inwhich said nozzle-means emits said spray.

l3. Charged-spray-producing means as defined in claim 11 but furthercharacterized by additional electrode-means spaced from each of saidelectrodes on a side of each of said electrodes which faces away fromsaid nozzle-tip, and voltage-applying means for oppositely charging saidnozzle-tip and said electrodes and for oppositely charging saidelectrode and electrodemeans, the spacing, configuration andchargingpotentials being such that the field gradient at said electrodesfacing in a direction toward said space is less than the field gradientat a part of said electrodes facing in a direction away from said space.

14. Charged-spray-producing means as defined in claim 13 but furthercharacterized by said electrodes being sloped from the direction inwhich said nozzle-means emits said spray.

15. Means for producing a charged spray comprising a pair oi elongatedrod-like substantially parallel electrodes, spray-nozzle-means having aspraying point insulated from said electrodes and providing a spray inthe space between said electrodes, and chargeable by an'electric fieldbetween said spraying point and said electrodes, said electrodes beinglengthwise substantially straight and transversely curved on the sidesfacing said spraying point, said spraying point being near a planenearest thereto that in- 7 8 cludes a part of each of said electrodes,said REFERENCES CITED spraying mint lying on side of said plane Thefollowing references are 01' record in the ing away from saidelectrodes, said electrodes me of this patent:

extending lengthwise beyond the nearest point of said sprayingnozzle-means for a distance UNITED STATES PATENTS greater than thedistance of said nearest point 5 Number Name Date to either of saidelectrodes- 1,958,406 Dariah May 15, 1934 16. charged-spray-producingmeans as de- 2,207,576 Brown July 9, 1940 fined in claim 15 but furthercharacterized by 2,357,354 Penney Sept. 5, 1944 pneumatic meansassociated with said nozzie- 10 means to provide a spray at saidspraying point.

SAMUEL GILMAN.

